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  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
  <title>Encrypted Media: Encryption Scheme Query</title>
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<style data-fill-with="stylesheet">/******************************************************************************
 *                   Style sheet for the W3C specifications                   *
 *
 * Special classes handled by this style sheet include:
 *
 * Indices
 *   - .toc for the Table of Contents (<ol class="toc">)
 *     + <span class="secno"> for the section numbers
 *   - #toc for the Table of Contents (<nav id="toc">)
 *   - ul.index for Indices (<a href="#ref">term</a><span>, in §N.M</span>)
 *   - table.index for Index Tables (e.g. for properties or elements)
 *
 * Structural Markup
 *   - table.data for general data tables
 *     -> use 'scope' attribute, <colgroup>, <thead>, and <tbody> for best results !
 *     -> use <table class='complex data'> for extra-complex tables
 *     -> use <td class='long'> for paragraph-length cell content
 *     -> use <td class='pre'> when manual line breaks/indentation would help readability
 *   - dl.switch for switch statements
 *   - ol.algorithm for algorithms (helps to visualize nesting)
 *   - .figure and .caption (HTML4) and figure and figcaption (HTML5)
 *     -> .sidefigure for right-floated figures
 *   - ins/del
 *
 * Code
 *   - pre and code
 *
 * Special Sections
 *   - .note       for informative notes             (div, p, span, aside, details)
 *   - .example    for informative examples          (div, p, pre, span)
 *   - .issue      for issues                        (div, p, span)
 *   - .assertion  for assertions                    (div, p, span)
 *   - .advisement for loud normative statements     (div, p, strong)
 *   - .annoying-warning for spec obsoletion notices (div, aside, details)
 *
 * Definition Boxes
 *   - pre.def   for WebIDL definitions
 *   - table.def for tables that define other entities (e.g. CSS properties)
 *   - dl.def    for definition lists that define other entitles (e.g. HTML elements)
 *
 * Numbering
 *   - .secno for section numbers in .toc and headings (<span class='secno'>3.2</span>)
 *   - .marker for source-inserted example/figure/issue numbers (<span class='marker'>Issue 4</span>)
 *   - ::before styled for CSS-generated issue/example/figure numbers:
 *     -> Documents wishing to use this only need to add
 *        figcaption::before,
 *        .caption::before { content: "Figure "  counter(figure) " ";  }
 *        .example::before { content: "Example " counter(example) " "; }
 *        .issue::before   { content: "Issue "   counter(issue) " ";   }
 *
 * Header Stuff (ignore, just don't conflict with these classes)
 *   - .head for the header
 *   - .copyright for the copyright
 *
 * Miscellaneous
 *   - .overlarge for things that should be as wide as possible, even if
 *     that overflows the body text area. This can be used on an item or
 *     on its container, depending on the effect desired.
 *     Note that this styling basically doesn't help at all when printing,
 *     since A4 paper isn't much wider than the max-width here.
 *     It's better to design things to fit into a narrower measure if possible.
 *   - js-added ToC jump links (see fixup.js)
 *
 ******************************************************************************/

/******************************************************************************/
/*                                   Body                                     */
/******************************************************************************/

	body {
		counter-reset: example figure issue;

		/* Layout */
		max-width: 50em;               /* limit line length to 50em for readability   */
		margin: 0 auto;                /* center text within page                     */
		padding: 1.6em 1.5em 2em 50px; /* assume 16px font size for downlevel clients */
		padding: 1.6em 1.5em 2em calc(26px + 1.5em); /* leave space for status flag     */

		/* Typography */
		line-height: 1.5;
		font-family: sans-serif;
		widows: 2;
		orphans: 2;
		word-wrap: break-word;
		overflow-wrap: break-word;
		hyphens: auto;

		/* Colors */
		color: black;
		background: white top left fixed no-repeat;
		background-size: 25px auto;
	}


/******************************************************************************/
/*                         Front Matter & Navigation                          */
/******************************************************************************/

/** Header ********************************************************************/

	div.head { margin-bottom: 1em }
	div.head hr { border-style: solid; }

	div.head h1 {
		font-weight: bold;
		margin: 0 0 .1em;
		font-size: 220%;
	}

	div.head h2 { margin-bottom: 1.5em;}

/** W3C Logo ******************************************************************/

	.head .logo {
		float: right;
		margin: 0.4rem 0 0.2rem .4rem;
	}

	.head img[src*="logos/W3C"] {
		display: block;
		border: solid #1a5e9a;
		border-width: .65rem .7rem .6rem;
		border-radius: .4rem;
		background: #1a5e9a;
		color: white;
		font-weight: bold;
	}

	.head a:hover > img[src*="logos/W3C"],
	.head a:focus > img[src*="logos/W3C"] {
		opacity: .8;
	}

	.head a:active > img[src*="logos/W3C"] {
		background: #c00;
		border-color: #c00;
	}

	/* see also additional rules in Link Styling section */

/** Copyright *****************************************************************/

	p.copyright,
	p.copyright small { font-size: small }

/** Back to Top / ToC Toggle **************************************************/

	@media print {
		#toc-nav {
			display: none;
		}
	}
	@media not print {
		#toc-nav {
			position: fixed;
			z-index: 2;
			bottom: 0; left: 0;
			margin: 0;
			min-width: 1.33em;
			border-top-right-radius: 2rem;
			box-shadow: 0 0 2px;
			font-size: 1.5em;
			color: black;
		}
		#toc-nav > a {
			display: block;
			white-space: nowrap;

			height: 1.33em;
			padding: .1em 0.3em;
			margin: 0;

			background: white;
			box-shadow: 0 0 2px;
			border: none;
			border-top-right-radius: 1.33em;
			background: white;
		}
		#toc-nav > #toc-jump {
			padding-bottom: 2em;
			margin-bottom: -1.9em;
		}

		#toc-nav > a:hover,
		#toc-nav > a:focus {
			background: #f8f8f8;
		}
		#toc-nav > a:not(:hover):not(:focus) {
			color: #707070;
		}

		/* statusbar gets in the way on keyboard focus; remove once browsers fix */
		#toc-nav > a[href="#toc"]:not(:hover):focus:last-child {
			padding-bottom: 1.5rem;
		}

		#toc-nav:not(:hover) > a:not(:focus) > span + span {
			/* Ideally this uses :focus-within on #toc-nav */
			display: none;
		}
		#toc-nav > a > span + span {
			padding-right: 0.2em;
		}

		#toc-toggle-inline {
			vertical-align: 0.05em;
			font-size: 80%;
			color: gray;
			color: hsla(203,20%,40%,.7);
			border-style: none;
			background: transparent;
			position: relative;
		}
		#toc-toggle-inline:hover:not(:active),
		#toc-toggle-inline:focus:not(:active) {
			text-shadow: 1px 1px silver;
			top: -1px;
			left: -1px;
		}

		#toc-nav :active {
			color: #C00;
		}
	}

/** ToC Sidebar ***************************************************************/

	/* Floating sidebar */
	@media screen {
		body.toc-sidebar #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			max-width: 80%;
			max-width: calc(100% - 2em - 26px);
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
		}
		body.toc-sidebar #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
		}
		body.toc-sidebar #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	/* Hide main scroller when only the ToC is visible anyway */
	@media screen and (max-width: 28em) {
		body.toc-sidebar {
			overflow: hidden;
		}
	}

	/* Sidebar with its own space */
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
		}
		body:not(.toc-inline) #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
		}

		body:not(.toc-inline) {
			padding-left: 29em;
		}
		/* See also Overflow section at the bottom */

		body:not(.toc-inline) #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) {
			margin: 0 4em;
		}
	}

/******************************************************************************/
/*                                Sectioning                                  */
/******************************************************************************/

/** Headings ******************************************************************/

	h1, h2, h3, h4, h5, h6, dt {
		page-break-after: avoid;
		page-break-inside: avoid;
		font: 100% sans-serif;   /* Reset all font styling to clear out UA styles */
		font-family: inherit;    /* Inherit the font family. */
		line-height: 1.2;        /* Keep wrapped headings compact */
		hyphens: manual;         /* Hyphenated headings look weird */
	}

	h2, h3, h4, h5, h6 {
		margin-top: 3rem;
	}

	h1, h2, h3 {
		color: #005A9C;
		background: transparent;
	}

	h1 { font-size: 170%; }
	h2 { font-size: 140%; }
	h3 { font-size: 120%; }
	h4 { font-weight: bold; }
	h5 { font-style: italic; }
	h6 { font-variant: small-caps; }
	dt { font-weight: bold; }

/** Subheadings ***************************************************************/

	h1 + h2,
	#subtitle {
		/* #subtitle is a subtitle in an H2 under the H1 */
		margin-top: 0;
	}
	h2 + h3,
	h3 + h4,
	h4 + h5,
	h5 + h6 {
		margin-top: 1.2em; /* = 1 x line-height */
	}

/** Section divider ***********************************************************/

	:not(.head) > hr {
		font-size: 1.5em;
		text-align: center;
		margin: 1em auto;
		height: auto;
		border: transparent solid 0;
		background: transparent;
	}
	:not(.head) > hr::before {
		content: "\2727\2003\2003\2727\2003\2003\2727";
	}

/******************************************************************************/
/*                            Paragraphs and Lists                            */
/******************************************************************************/

	p {
		margin: 1em 0;
	}

	dd > p:first-child,
	li > p:first-child {
		margin-top: 0;
	}

	ul, ol {
		margin-left: 0;
		padding-left: 2em;
	}

	li {
		margin: 0.25em 0 0.5em;
		padding: 0;
	}

	dl dd {
		margin: 0 0 .5em 2em;
	}

	.head dd + dd { /* compact for header */
		margin-top: -.5em;
	}

	/* Style for algorithms */
	ol.algorithm ol:not(.algorithm),
	.algorithm > ol ol:not(.algorithm) {
	 border-left: 0.5em solid #DEF;
	}

	/* Put nice boxes around each algorithm. */
	[data-algorithm]:not(.heading) {
	  padding: .5em;
	  border: thin solid #ddd; border-radius: .5em;
	  margin: .5em calc(-0.5em - 1px);
	}
	[data-algorithm]:not(.heading) > :first-child {
	  margin-top: 0;
	}
	[data-algorithm]:not(.heading) > :last-child {
	  margin-bottom: 0;
	}

	/* Style for switch/case <dl>s */
	dl.switch > dd > ol.only,
	dl.switch > dd > .only > ol {
	 margin-left: 0;
	}
	dl.switch > dd > ol.algorithm,
	dl.switch > dd > .algorithm > ol {
	 margin-left: -2em;
	}
	dl.switch {
	 padding-left: 2em;
	}
	dl.switch > dt {
	 text-indent: -1.5em;
	 margin-top: 1em;
	}
	dl.switch > dt + dt {
	 margin-top: 0;
	}
	dl.switch > dt::before {
	 content: '\21AA';
	 padding: 0 0.5em 0 0;
	 display: inline-block;
	 width: 1em;
	 text-align: right;
	 line-height: 0.5em;
	}

/** Terminology Markup ********************************************************/


/******************************************************************************/
/*                                 Inline Markup                              */
/******************************************************************************/

/** Terminology Markup ********************************************************/
	dfn   { /* Defining instance */
		font-weight: bolder;
	}
	a > i { /* Instance of term */
		font-style: normal;
	}
	dt dfn code, code.idl {
		font-size: medium;
	}
	dfn var {
		font-style: normal;
	}

/** Change Marking ************************************************************/

	del { color: red;  text-decoration: line-through; }
	ins { color: #080; text-decoration: underline;    }

/** Miscellaneous improvements to inline formatting ***************************/

	sup {
		vertical-align: super;
		font-size: 80%
	}

/******************************************************************************/
/*                                    Code                                    */
/******************************************************************************/

/** General monospace/pre rules ***********************************************/

	pre, code, samp {
		font-family: Menlo, Consolas, "DejaVu Sans Mono", Monaco, monospace;
		font-size: .9em;
		page-break-inside: avoid;
		hyphens: none;
		text-transform: none;
	}
	pre code,
	code code {
		font-size: 100%;
	}

	pre {
		margin-top: 1em;
		margin-bottom: 1em;
		overflow: auto;
	}

/** Inline Code fragments *****************************************************/

  /* Do something nice. */

/******************************************************************************/
/*                                    Links                                   */
/******************************************************************************/

/** General Hyperlinks ********************************************************/

	/* We hyperlink a lot, so make it less intrusive */
	a[href] {
		color: #034575;
		text-decoration: none;
		border-bottom: 1px solid #707070;
		/* Need a bit of extending for it to look okay */
		padding: 0 1px 0;
		margin: 0 -1px 0;
	}
	a:visited {
		border-bottom-color: #BBB;
	}

	/* Use distinguishing colors when user is interacting with the link */
	a[href]:focus,
	a[href]:hover {
		background: #f8f8f8;
		background: rgba(75%, 75%, 75%, .25);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	a[href]:active {
		color: #C00;
		border-color: #C00;
	}

	/* Backout above styling for W3C logo */
	.head .logo,
	.head .logo a {
		border: none;
		text-decoration: none;
		background: transparent;
	}

/******************************************************************************/
/*                                    Images                                  */
/******************************************************************************/

	img {
		border-style: none;
	}

	/* For autogen numbers, add
	   .caption::before, figcaption::before { content: "Figure " counter(figure) ". "; }
	*/

	figure, .figure, .sidefigure {
		page-break-inside: avoid;
		text-align: center;
		margin: 2.5em 0;
	}
	.figure img,    .sidefigure img,    figure img,
	.figure object, .sidefigure object, figure object {
		max-width: 100%;
		margin: auto;
	}
	.figure pre, .sidefigure pre, figure pre {
		text-align: left;
		display: table;
		margin: 1em auto;
	}
	.figure table, figure table {
		margin: auto;
	}
	@media screen and (min-width: 20em) {
		.sidefigure {
			float: right;
			width: 50%;
			margin: 0 0 0.5em 0.5em
		}
	}
	.caption, figcaption, caption {
		font-style: italic;
		font-size: 90%;
	}
	.caption::before, figcaption::before, figcaption > .marker {
		font-weight: bold;
	}
	.caption, figcaption {
		counter-increment: figure;
	}

	/* DL list is indented 2em, but figure inside it is not */
	dd > .figure, dd > figure { margin-left: -2em }

/******************************************************************************/
/*                             Colored Boxes                                  */
/******************************************************************************/

	.issue, .note, .example, .assertion, .advisement, blockquote {
		padding: .5em;
		border: .5em;
		border-left-style: solid;
		page-break-inside: avoid;
	}
	span.issue, span.note {
		padding: .1em .5em .15em;
		border-right-style: solid;
	}

	.issue,
	.note,
	.example,
	.advisement,
	.assertion,
	blockquote {
		margin: 1em auto;
	}
	.note  > p:first-child,
	.issue > p:first-child,
	blockquote > :first-child {
		margin-top: 0;
	}
	blockquote > :last-child {
		margin-bottom: 0;
	}

/** Blockquotes ***************************************************************/

	blockquote {
		border-color: silver;
	}

/** Open issue ****************************************************************/

	.issue {
		border-color: #E05252;
		background: #FBE9E9;
		counter-increment: issue;
		overflow: auto;
	}
	.issue::before, .issue > .marker {
		text-transform: uppercase;
		color: #AE1E1E;
		padding-right: 1em;
		text-transform: uppercase;
	}
	/* Add .issue::before { content: "Issue " counter(issue) " "; } for autogen numbers,
	   or use class="marker" to mark up the issue number in source. */

/** Example *******************************************************************/

	.example {
		border-color: #E0CB52;
		background: #FCFAEE;
		counter-increment: example;
		overflow: auto;
		clear: both;
	}
	.example::before, .example > .marker {
		text-transform: uppercase;
		color: #827017;
		min-width: 7.5em;
		display: block;
	}
	/* Add .example::before { content: "Example " counter(example) " "; } for autogen numbers,
	   or use class="marker" to mark up the example number in source. */

/** Non-normative Note ********************************************************/

	.note {
		border-color: #52E052;
		background: #E9FBE9;
		overflow: auto;
	}

	.note::before, .note > .marker,
	details.note > summary::before,
	details.note > summary > .marker {
		text-transform: uppercase;
		display: block;
		color: hsl(120, 70%, 30%);
	}
	/* Add .note::before { content: "Note"; } for autogen label,
	   or use class="marker" to mark up the label in source. */

	details.note > summary {
		display: block;
		color: hsl(120, 70%, 30%);
	}
	details.note[open] > summary {
		border-bottom: 1px silver solid;
	}

/** Assertion Box *************************************************************/
	/*  for assertions in algorithms */

	.assertion {
		border-color: #AAA;
		background: #EEE;
	}

/** Advisement Box ************************************************************/
	/*  for attention-grabbing normative statements */

	.advisement {
		border-color: orange;
		border-style: none solid;
		background: #FFEECC;
	}
	strong.advisement {
		display: block;
		text-align: center;
	}
	.advisement > .marker {
		color: #B35F00;
	}

/** Spec Obsoletion Notice ****************************************************/
	/* obnoxious obsoletion notice for older/abandoned specs. */

	details {
		display: block;
	}
	summary {
		font-weight: bolder;
	}

	.annoying-warning:not(details),
	details.annoying-warning:not([open]) > summary,
	details.annoying-warning[open] {
		background: #fdd;
		color: red;
		font-weight: bold;
		padding: .75em 1em;
		border: thick red;
		border-style: solid;
		border-radius: 1em;
	}
	.annoying-warning :last-child {
		margin-bottom: 0;
	}

@media not print {
	details.annoying-warning[open] {
		position: fixed;
		left: 1em;
		right: 1em;
		bottom: 1em;
		z-index: 1000;
	}
}

	details.annoying-warning:not([open]) > summary {
		text-align: center;
	}

/** Entity Definition Boxes ***************************************************/

	.def {
		padding: .5em 1em;
		background: #DEF;
		margin: 1.2em 0;
		border-left: 0.5em solid #8CCBF2;
	}

/******************************************************************************/
/*                                    Tables                                  */
/******************************************************************************/

	th, td {
		text-align: left;
		text-align: start;
	}

/** Property/Descriptor Definition Tables *************************************/

	table.def {
		/* inherits .def box styling, see above */
		width: 100%;
		border-spacing: 0;
	}

	table.def td,
	table.def th {
		padding: 0.5em;
		vertical-align: baseline;
		border-bottom: 1px solid #bbd7e9;
	}

	table.def > tbody > tr:last-child th,
	table.def > tbody > tr:last-child td {
		border-bottom: 0;
	}

	table.def th {
		font-style: italic;
		font-weight: normal;
		padding-left: 1em;
		width: 3em;
	}

	/* For when values are extra-complex and need formatting for readability */
	table td.pre {
		white-space: pre-wrap;
	}

	/* A footnote at the bottom of a def table */
	table.def           td.footnote {
		padding-top: 0.6em;
	}
	table.def           td.footnote::before {
		content: " ";
		display: block;
		height: 0.6em;
		width: 4em;
		border-top: thin solid;
	}

/** Data tables (and properly marked-up index tables) *************************/
	/*
		 <table class="data"> highlights structural relationships in a table
		 when correct markup is used (e.g. thead/tbody, th vs. td, scope attribute)

		 Use class="complex data" for particularly complicated tables --
		 (This will draw more lines: busier, but clearer.)

		 Use class="long" on table cells with paragraph-like contents
		 (This will adjust text alignment accordingly.)
		 Alternately use class="longlastcol" on tables, to have the last column assume "long".
	*/

	table {
		word-wrap: normal;
		overflow-wrap: normal;
		hyphens: manual;
	}

	table.data,
	table.index {
		margin: 1em auto;
		border-collapse: collapse;
		border: hidden;
		width: 100%;
	}
	table.data caption,
	table.index caption {
		max-width: 50em;
		margin: 0 auto 1em;
	}

	table.data td,  table.data th,
	table.index td, table.index th {
		padding: 0.5em 1em;
		border-width: 1px;
		border-color: silver;
		border-top-style: solid;
	}

	table.data thead td:empty {
		padding: 0;
		border: 0;
	}

	table.data  thead,
	table.index thead,
	table.data  tbody,
	table.index tbody {
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/******************************************************************************/
/*                                  Indices                                   */
/******************************************************************************/


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/*                                    Print                                   */
/******************************************************************************/

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/******************************************************************************/
/*                                    Legacy                                  */
/******************************************************************************/

	/* This rule is inherited from past style sheets. No idea what it's for. */
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/******************************************************************************/
/*                             Overflow Control                               */
/******************************************************************************/

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 <body class="h-entry">
  <div class="head">
   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref" id="title">Encrypted Media: Encryption Scheme Query</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Draft Community Group Report, <time class="dt-updated" datetime="1970-01-01">1 January 1970</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt>This version:
     <dd><a class="u-url" href="https://wicg.github.io/encrypted-media-encryption-scheme/">https://wicg.github.io/encrypted-media-encryption-scheme/</a>
     <dt class="editor">Editors:
     <dd class="editor p-author h-card vcard" data-editor-id="105371"><span class="p-name fn">Joey Parrish</span> (<a class="p-org org" href="https://google.com/">Google Inc.</a>)
     <dd class="editor p-author h-card vcard"><span class="p-name fn"></span>
     <dt>Participate:
     <dd><a href="https://github.com/wicg/encrypted-media-encryption-scheme">Git Repository.</a>
     <dd><a href="https://github.com/wicg/encrypted-media-encryption-scheme/issues/new">File an issue.</a>
     <dt>Version History:
     <dd><a href="https://github.com/wicg/encrypted-media-encryption-scheme/commits">https://github.com/wicg/encrypted-media-encryption-scheme/commits</a>
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 1970 the Contributors to the Encrypted Media: Encryption Scheme Query Specification, published by the <a href="https://www.w3.org/community/wicg/">Web Platform Incubator Community Group</a> under the <a href="https://www.w3.org/community/about/agreements/cla/">W3C Community Contributor License Agreement (CLA)</a>.
A human-readable <a href="http://www.w3.org/community/about/agreements/cla-deed/">summary</a> is available. </p>
   <hr title="Separator for header">
  </div>
  <div class="p-summary" data-fill-with="abstract">
   <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
   <p>This is an extension to the W3C Encrypted Media Extensions

specification, to be integrated into EME vNext. The API will allow
authors to query support for specific encryption schemes in the CDM.</p>
  </div>
  <div data-fill-with="at-risk"></div>
  <h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
  <div data-fill-with="status">
   <p> This specification was published by the <a href="https://www.w3.org/community/wicg/">Web Platform Incubator Community Group</a>.
  It is not a W3C Standard nor is it on the W3C Standards Track.

  Please note that under the <a href="https://www.w3.org/community/about/agreements/cla/">W3C Community Contributor License Agreement (CLA)</a> there is a limited opt-out and other conditions apply.

  Learn more about <a href="http://www.w3.org/community/">W3C Community and Business Groups</a>. </p>
   <p></p>
  </div>
  <div data-fill-with="at-risk"></div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li><a href="#mediakeysystemmediacapability-extension"><span class="secno">1</span> <span class="content"> MediaKeySystemMediaCapability dictionary extension </span></a>
    <li><a href="#algorithm-extension"><span class="secno">2</span> <span class="content"> Algorithm Extensions </span></a>
    <li><a href="#clearkey-requirements"><span class="secno">3</span> <span class="content"> Clear Key Requirements </span></a>
    <li><a href="#application-notes"><span class="secno">4</span> <span class="content"> Application Notes </span></a>
    <li><a href="#polyfills"><span class="secno">5</span> <span class="content"> Polyfills and Backward Compatibility </span></a>
    <li>
     <a href="#security-privacy-considerations"><span class="secno">6</span> <span class="content"> Security and Privacy Considerations </span></a>
     <ol class="toc">
      <li><a href="#fingerprinting"><span class="secno">6.1</span> <span class="content"> Fingerprinting </span></a>
      <li><a href="#user-consent"><span class="secno">6.2</span> <span class="content"> User Consent </span></a>
     </ol>
    <li><a href="#examples"><span class="secno">7</span> <span class="content">Examples</span></a>
    <li><a href="#conformance"><span class="secno"></span> <span class="content"> Conformance</span></a>
    <li>
     <a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
     <ol class="toc">
      <li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
      <li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
     </ol>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
     </ol>
    <li><a href="#idl-index"><span class="secno"></span> <span class="content">IDL Index</span></a>
    <li><a href="#issues-index"><span class="secno"></span> <span class="content">Issues Index</span></a>
   </ol>
  </nav>
  <main>
   <section>
    <h2 class="heading settled" data-level="1" id="mediakeysystemmediacapability-extension"><span class="secno">1. </span><span class="content"> MediaKeySystemMediaCapability dictionary extension </span><a class="self-link" href="#mediakeysystemmediacapability-extension"></a></h2>
<pre class="idl highlight def"><c- b>partial</c-> <c- b>dictionary</c-> <a class="idl-code" data-link-type="dictionary"><c- g>MediaKeySystemMediaCapability</c-></a> {
  <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString"><c- b>DOMString</c-></a>? <dfn class="dfn-paneled idl-code" data-default="null" data-dfn-for="MediaKeySystemMediaCapability" data-dfn-type="dict-member" data-export data-type="DOMString? " id="dom-mediakeysystemmediacapability-encryptionscheme"><code><c- g>encryptionScheme</c-></code></dfn> = <c- b>null</c->;
};
</pre>
    <p> The <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme">encryptionScheme</a></code> field indicates an encryption scheme required by
    the application in combination with the other fields of the <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemmediacapability" id="ref-for-dom-mediakeysystemmediacapability">MediaKeySystemMediaCapability</a></code> dictionary.  A value which is null or <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-present" id="ref-for-dfn-present">not present</a> indicates to the user agent that no specific encryption
    scheme is required by the application, and therefore any encryption scheme
    is acceptable. </p>
    <p class="note" role="note"><span>NOTE:</span> Applications that are aware of this field should always specify a
    value.  See <a href="#application-notes">§ 4 Application Notes</a> for details.</p>
    <p class="note" role="note"><span>NOTE:</span> If <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme①">encryptionScheme</a></code> is <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-present" id="ref-for-dfn-present①">not present</a>, the <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme②">encryptionScheme</a></code> field of the <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemmediacapability" id="ref-for-dom-mediakeysystemmediacapability①">MediaKeySystemMediaCapability</a></code> object
    returned from <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess" id="ref-for-dom-mediakeysystemaccess">MediaKeySystemAccess</a></code>.<code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess-getconfiguration" id="ref-for-dom-mediakeysystemaccess-getconfiguration">getConfiguration()</a></code> must be <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-present" id="ref-for-dfn-present②">present</a> and set to the default value of null.  This enables detection
    of this feature in polyfills for user agents which do not support this
    field.  See also <a href="#polyfills">§ 5 Polyfills and Backward Compatibility</a>.</p>
    <p class="note" role="note"><span>NOTE:</span> The empty string is distinct from null or <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-present" id="ref-for-dfn-present③">not present</a>, and so
    would be treated as an unrecognized encryption scheme.</p>
    <p>Well-known values for <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme③">encryptionScheme</a></code> are:</p>
    <ul>
     <li data-md>
      <p><dfn class="dfn-paneled" data-dfn-type="dfn" data-noexport id="cenc">cenc</dfn>: The "cenc" mode, defined in ISO 23001-7:2016, section
               4.2a.  AES-CTR mode full sample and video NAL
               subsample encryption.</p>
     <li data-md>
      <p><dfn data-dfn-type="dfn" data-noexport id="cbcs">cbcs<a class="self-link" href="#cbcs"></a></dfn>: The "cbcs" mode, defined in ISO 23001-7:2016, section
               4.2d.  AES-CBC mode partial video NAL pattern
               encryption.  For video, the spec allows various
               encryption patterns.</p>
     <li data-md>
      <p><dfn data-dfn-type="dfn" data-noexport id="cbcs-1-9">cbcs-1-9<a class="self-link" href="#cbcs-1-9"></a></dfn>: The same as "cbcs" mode, but with a specific
                   encrypt:skip pattern of 1:9 for video, as
                   recommended in ISO 23001-7:2016, section 10.4.2.</p>
    </ul>
    <p class="note" role="note"><span>NOTE:</span> The document WebM Encryption defines WebM encryption to be equivalent
          to and compatible with the "cenc" encryption mode defined in ISO
          23001-7:2016.</p>
    <p class="issue" id="issue-7472f44c"><a class="self-link" href="#issue-7472f44c"></a> A registry should be created for encryption schemes, and the
    existing format registry should be updated with respect to encryption
    schemes. <a href="https://github.com/wicg/encrypted-media-encryption-scheme/issues/#9">&lt;https://github.com/wicg/encrypted-media-encryption-scheme/issues/#9></a></p>
    <p></p>
   </section>
   <section>
    <h2 class="heading settled" data-level="2" id="algorithm-extension"><span class="secno">2. </span><span class="content"> Algorithm Extensions </span><a class="self-link" href="#algorithm-extension"></a></h2>
    <p> In the <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#get-supported-capabilities-for-audio-video-type" id="ref-for-get-supported-capabilities-for-audio-video-type">Get Supported Capabilities...</a></code> algorithm, the following changes
    should be made: </p>
    <ol>
     <li data-md>
      <p>In the loop that begins with "For each <var>requested media
capability</var> in <var> requested media capabilities</var>",
the user agent MUST run the following steps at the beginning of the
loop:</p>
      <ol>
       <li data-md>
        <p>Let <var>encryption scheme</var> be <var>requested media capability</var>’s <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme④">encryptionScheme</a></code> member.</p>
       <li data-md>
        <p>If <var>encryption scheme</var> is non-null and is not recognized or not
supported by the user agent, continue to the next iteration.</p>
      </ol>
     <li data-md>
      <p>In the step that says "If the user agent and <var>implementation</var> definitely
support playback of encrypted <a data-link-type="dfn" href="https://www.w3.org/TR/html51/semantics-embedded-content.html#media-data" id="ref-for-media-data">media data</a> for the combination of <var>container</var>, <var>media types</var>, <var>robustness</var> and <var>local accumulated
configuration</var> in combination with <var>restrictions</var>", the user agent MUST
replace the condition with the following condition:</p>
      <ol>
       <li data-md>
        <p>If the user agent and <var>implementation</var> definitely support playback of
encrypted <a data-link-type="dfn" href="https://www.w3.org/TR/html51/semantics-embedded-content.html#media-data" id="ref-for-media-data①">media data</a> for the combination of <var>container</var>, <var>media types</var>, <var>robustness</var>, <var>encryption scheme</var>, and <var>local
accumulated configuration</var> in combination with <var>restrictions</var>...</p>
      </ol>
    </ol>
    <p></p>
   </section>
   <section>
    <h2 class="heading settled" data-level="3" id="clearkey-requirements"><span class="secno">3. </span><span class="content"> Clear Key Requirements </span><a class="self-link" href="#clearkey-requirements"></a></h2>
    <p> <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#clear-key" id="ref-for-clear-key">Clear Key</a></code> implementations MUST support the <a data-link-type="dfn" href="#cenc" id="ref-for-cenc">cenc</a> scheme at a
    minimum, to ensure interoperability for users of this common key system. </p>
   </section>
   <section class="non-normative">
    <h2 class="heading settled" data-level="4" id="application-notes"><span class="secno">4. </span><span class="content"> Application Notes </span><a class="self-link" href="#application-notes"></a></h2>
    <p> Applications that are aware of the <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑤">encryptionScheme</a></code> field should always
    specify the encryption scheme(s) they require, since different encryption
    schemes are generally incompatible with one another.  It is unrealistic for
    an application to be accepting of "any" encryption scheme, but the default
    of null and the interpretation of null as "any" provide backward
    compatibility for unaware applications and a path to a polyfill for older
    user agents.  See also <a href="#polyfills">§ 5 Polyfills and Backward Compatibility</a>. </p>
    <p> Applications may specify multiple encryption schemes in separate <a href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemconfiguration">configurations</a>, or in
    multiple <a href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemmediacapability">capabilities</a> of the same configuration. </p>
    <p> The user agent only selects one configuration.  So if different encryption
    schemes are specified in separate configurations, the application will be
    given back a configuration containing only one encryption scheme. </p>
    <p> If different encryption schemes appear in the same configuration, the user
    agent’s accumulated configuration will contain the supported subset of the
    capabilities specified by the application.  The configuration returned from <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess-getconfiguration" id="ref-for-dom-mediakeysystemaccess-getconfiguration①">getConfiguration()</a></code> may therefore contain more than one encryption
    scheme. </p>
   </section>
   <section class="non-normative">
    <h2 class="heading settled" data-level="5" id="polyfills"><span class="secno">5. </span><span class="content"> Polyfills and Backward Compatibility </span><a class="self-link" href="#polyfills"></a></h2>
    <p> Omission of <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑥">encryptionScheme</a></code> is supported only to maintain backward
    compatibility for applications that are unaware of this field.  Applications
    should always specify the encryption scheme(s) they require.  See also <a href="#application-notes">§ 4 Application Notes</a>. </p>
    <p> Applications which do not specify <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑦">encryptionScheme</a></code> will get the same
    behavior they did before this feature existed: encryption scheme will not be
    considered during <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#navigator-extension:-requestmediakeysystemaccess()" id="ref-for-navigator-extension:-requestmediakeysystemaccess()">requestMediaKeySystemAccess()</a></code>, and they will have to
    make assumptions about which encryption scheme(s) the user agent supports. </p>
    <p> User agents which implement this specification will always have an <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑧">encryptionScheme</a></code> field in the <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemmediacapability" id="ref-for-dom-mediakeysystemmediacapability②">MediaKeySystemMediaCapability</a></code> object
    returned from <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess" id="ref-for-dom-mediakeysystemaccess①">MediaKeySystemAccess</a></code>.<code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess-getconfiguration" id="ref-for-dom-mediakeysystemaccess-getconfiguration②">getConfiguration()</a></code>, even if the
    field is <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-present" id="ref-for-dfn-present④">not present</a> in the <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemmediacapability" id="ref-for-dom-mediakeysystemmediacapability③">MediaKeySystemMediaCapability</a></code> object
    given by the application.  This enables a <a href="https://remysharp.com/2010/10/08/what-is-a-polyfill">polyfill</a> to be written which detects the lack of <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑨">encryptionScheme</a></code> to determine
    whether or not a browser supports it. </p>
    <p> If the user agent does not support the <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme①⓪">encryptionScheme</a></code> field, a
    polyfill can use assumptions about the encryption scheme(s) supported by
    various user agents to emulate this specification and reject <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemmediacapability" id="ref-for-dom-mediakeysystemmediacapability④">MediaKeySystemMediaCapability</a></code> objects which specify (assumed)
    unsupported schemes.  Note that these are the same assumptions already made
    by existing applications.  A polyfill would allow an application to offload
    those assumptions.  The application could then always use the <code class="idl"><a data-link-type="idl" href="#dom-mediakeysystemmediacapability-encryptionscheme" id="ref-for-dom-mediakeysystemmediacapability-encryptionscheme①①">encryptionScheme</a></code> field to specify their needs using a standard API. </p>
    <p class="issue" id="issue-74d893e8"><a class="self-link" href="#issue-74d893e8"></a> Publish and link to a polyfill for this feature. <a href="https://github.com/wicg/encrypted-media-encryption-scheme/issues/#13">&lt;https://github.com/wicg/encrypted-media-encryption-scheme/issues/#13></a></p>
    <p> Any user agent which deprecates support for an existing encryption scheme
    could introduce backward compatibility issues for older applications which
    do not use this new feature.  Appropriate communication with developers will
    be necessary to ensure that applications are updated in a timely manner
    ahead of any such deprecation.  The need for good communication around
    deprecations is not unique to this proposal. </p>
   </section>
   <section class="non-normative">
    <h2 class="heading settled" data-level="6" id="security-privacy-considerations"><span class="secno">6. </span><span class="content"> Security and Privacy Considerations </span><a class="self-link" href="#security-privacy-considerations"></a></h2>
    <section>
     <p> This specification does not introduce any security-sensitive information
      or APIs. </p>
     <section>
      <h3 class="heading settled" data-level="6.1" id="fingerprinting"><span class="secno">6.1. </span><span class="content"> Fingerprinting </span><a class="self-link" href="#fingerprinting"></a></h3>
      <p> This extension offers an additional field an application can use to
        determine the device’s decryption capabilities.  This does not increase
        the fingerprint surface by much, since decryption capabilities are
        generally the same for any given user agent and operating system.  This
        extension simply offers applications a way to avoid hard-coding this
        knowledge. </p>
     </section>
     <section>
      <h3 class="heading settled" data-level="6.2" id="user-consent"><span class="secno">6.2. </span><span class="content"> User Consent </span><a class="self-link" href="#user-consent"></a></h3>
      <p> Fingerprinting concerns are mitigated by the fact that this new field is
        part of the <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/encrypted-media/#navigator-extension:-requestmediakeysystemaccess()" id="ref-for-navigator-extension:-requestmediakeysystemaccess()①">requestMediaKeySystemAccess()</a></code> API, which
        may require user consent.  User agents that would require user consent
        in order to access the CDM will therefore require user consent to make
        use of this new field. </p>
     </section>
    </section>
   </section>
   <section>
    <h2 class="heading settled" data-level="7" id="examples"><span class="secno">7. </span><span class="content">Examples</span><a class="self-link" href="#examples"></a></h2>
    <div class="example" id="example-a675a946">
     <a class="self-link" href="#example-a675a946"></a> 
<pre class="highlight"><c- a>function</c-> tryTwoEncryptionSchemesInSeparateConfigurations<c- p>(</c->keySystem<c- p>)</c-> <c- p>{</c->
  <c- c1>// Query two configurations with different encryption schemes.</c->
  <c- c1>// Only one will be chosen by the user agent.</c->

  <c- k>return</c-> navigator<c- p>.</c->requestMediaKeySystemAccess<c- p>(</c->keySystem<c- p>,</c-> <c- p>[</c->
    <c- p>{</c-> <c- c1>// A configuration which uses the "cenc" encryption scheme</c->
      videoCapabilities<c- o>:</c-> <c- p>[{</c->
        contentType<c- o>:</c-> <c- t>'video/mp4; codecs="avc1.640028"'</c-><c- p>,</c->
        encryptionScheme<c- o>:</c-> <c- t>'cenc'</c-><c- p>,</c->
      <c- p>}],</c->
      audioCapabilities<c- o>:</c-> <c- p>[{</c->
        contentType<c- o>:</c-> <c- t>'audio/mp4; codecs="mp4a.40.2"'</c-><c- p>,</c->
        encryptionScheme<c- o>:</c-> <c- t>'cenc'</c-><c- p>,</c->
      <c- p>}],</c->
      initDataTypes<c- o>:</c-> <c- p>[</c-><c- t>'keyids'</c-><c- p>],</c->
    <c- p>},</c->

    <c- p>{</c-> <c- c1>// A configuration which uses the "cbcs-1-9" encryption scheme</c->
      videoCapabilities<c- o>:</c-> <c- p>[{</c->
        contentType<c- o>:</c-> <c- t>'video/mp4; codecs="avc1.640028"'</c-><c- p>,</c->
        encryptionScheme<c- o>:</c-> <c- t>'cbcs-1-9'</c-><c- p>,</c->
      <c- p>}],</c->
      audioCapabilities<c- o>:</c-> <c- p>[{</c->
        contentType<c- o>:</c-> <c- t>'audio/mp4; codecs="mp4a.40.2"'</c-><c- p>,</c->
        encryptionScheme<c- o>:</c-> <c- t>'cbcs-1-9'</c-><c- p>,</c->
      <c- p>}],</c->
      initDataTypes<c- o>:</c-> <c- p>[</c-><c- t>'keyids'</c-><c- p>],</c->
    <c- p>},</c->
  <c- p>]);</c->
<c- p>}</c->
</pre>
    </div>
    <div class="example" id="example-636e32dd">
     <a class="self-link" href="#example-636e32dd"></a> 
<pre class="highlight"><c- a>function</c-> tryTwoEncryptionSchemesInOneConfiguration<c- p>(</c->keySystem<c- p>)</c-> <c- p>{</c->
  <c- c1>// Query one configuration with two different encryption schemes.</c->
  <c- c1>// The user agent will eliminate any capabilities object it cannot support,</c->
  <c- c1>// so the accumulated configuration may contain one encryption scheme or both.</c->

  <c- k>return</c-> navigator<c- p>.</c->requestMediaKeySystemAccess<c- p>(</c->keySystem<c- p>,</c-> <c- p>[{</c->
    videoCapabilities<c- o>:</c-> <c- p>[</c->
      <c- p>{</c-> <c- c1>// A capability object which uses the "cenc" encryption scheme</c->
        contentType<c- o>:</c-> <c- t>'video/mp4; codecs="avc1.640028"'</c-><c- p>,</c->
        encryptionScheme<c- o>:</c-> <c- t>'cenc'</c-><c- p>,</c->
      <c- p>},</c->
      <c- p>{</c-> <c- c1>// A capability object which uses the "cbcs-1-9" encryption</c->
        <c- c1>// scheme</c->
        contentType<c- o>:</c-> <c- t>'video/mp4; codecs="avc1.640028"'</c-><c- p>,</c->
        encryptionScheme<c- o>:</c-> <c- t>'cbcs-1-9'</c-><c- p>,</c->
      <c- p>},</c->
    <c- p>],</c->
    audioCapabilities<c- o>:</c-> <c- p>[</c->
      <c- p>{</c-> <c- c1>// A capability object which uses the "cenc" encryption scheme</c->
        contentType<c- o>:</c-> <c- t>'audio/mp4; codecs="mp4a.40.2"'</c-><c- p>,</c->
        encryptionScheme<c- o>:</c-> <c- t>'cenc'</c-><c- p>,</c->
      <c- p>},</c->
      <c- p>{</c-> <c- c1>// A capability object which uses the "cbcs-1-9" encryption</c->
        <c- c1>// scheme</c->
        contentType<c- o>:</c-> <c- t>'audio/mp4; codecs="mp4a.40.2"'</c-><c- p>,</c->
        encryptionScheme<c- o>:</c-> <c- t>'cbcs-1-9'</c-><c- p>,</c->
      <c- p>},</c->
    <c- p>],</c->
    initDataTypes<c- o>:</c-> <c- p>[</c-><c- t>'keyids'</c-><c- p>],</c->
  <c- p>}]);</c->
<c- p>}</c->
</pre>
    </div>
   </section>
  </main>
  <div data-fill-with="conformance">
   <h2 class="no-ref no-num heading settled" id="conformance"><span class="content"> Conformance</span><a class="self-link" href="#conformance"></a></h2>
   <p> Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology.
            The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL”
            in the normative parts of this document
            are to be interpreted as described in RFC 2119.
            However, for readability,
            these words do not appear in all uppercase letters in this specification. </p>
   <p> All of the text of this specification is normative
            except sections explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a> </p>
   <p> Examples in this specification are introduced with the words “for example”
            or are set apart from the normative text with <code>class="example"</code>, like this: </p>
   <div class="example" id="example-example"><a class="self-link" href="#example-example"></a> This is an example of an informative example. </div>
   <p> Informative notes begin with the word “Note”
            and are set apart from the normative text with <code>class="note"</code>, like this: </p>
   <p class="note" role="note"> Note, this is an informative note. </p>
  </div>
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      document.body.classList.remove('toc-inline');
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        window.scrollBy(0, 0 - tocHeight);
      }
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      document.body.classList.remove('toc-sidebar');
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      }
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  }

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      tocNav.id = 'toc-nav';
      /* Prepend for better keyboard navigation */
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    }
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  <h2 class="no-num no-ref heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
  <h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="content">Terms defined by this specification</span><a class="self-link" href="#index-defined-here"></a></h3>
  <ul class="index">
   <li><a href="#cbcs">cbcs</a><span>, in §1</span>
   <li><a href="#cbcs-1-9">cbcs-1-9</a><span>, in §1</span>
   <li><a href="#cenc">cenc</a><span>, in §1</span>
   <li><a href="#dom-mediakeysystemmediacapability-encryptionscheme">encryptionScheme</a><span>, in §1</span>
  </ul>
  <aside class="dfn-panel" data-for="term-for-clear-key">
   <a href="https://www.w3.org/TR/encrypted-media/#clear-key">https://www.w3.org/TR/encrypted-media/#clear-key</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-clear-key">3. 
    Clear Key Requirements </a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-get-supported-capabilities-for-audio-video-type">
   <a href="https://www.w3.org/TR/encrypted-media/#get-supported-capabilities-for-audio-video-type">https://www.w3.org/TR/encrypted-media/#get-supported-capabilities-for-audio-video-type</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-get-supported-capabilities-for-audio-video-type">2. 
    Algorithm Extensions </a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-dom-mediakeysystemaccess">
   <a href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess">https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-mediakeysystemaccess">1. 
    MediaKeySystemMediaCapability dictionary extension </a>
    <li><a href="#ref-for-dom-mediakeysystemaccess①">5. 
    Polyfills and Backward Compatibility </a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-dom-mediakeysystemmediacapability">
   <a href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemmediacapability">https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemmediacapability</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-mediakeysystemmediacapability">1. 
    MediaKeySystemMediaCapability dictionary extension </a> <a href="#ref-for-dom-mediakeysystemmediacapability①">(2)</a>
    <li><a href="#ref-for-dom-mediakeysystemmediacapability②">5. 
    Polyfills and Backward Compatibility </a> <a href="#ref-for-dom-mediakeysystemmediacapability③">(2)</a> <a href="#ref-for-dom-mediakeysystemmediacapability④">(3)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-dom-mediakeysystemaccess-getconfiguration">
   <a href="https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess-getconfiguration">https://www.w3.org/TR/encrypted-media/#dom-mediakeysystemaccess-getconfiguration</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-mediakeysystemaccess-getconfiguration">1. 
    MediaKeySystemMediaCapability dictionary extension </a>
    <li><a href="#ref-for-dom-mediakeysystemaccess-getconfiguration①">4. 
    Application Notes </a>
    <li><a href="#ref-for-dom-mediakeysystemaccess-getconfiguration②">5. 
    Polyfills and Backward Compatibility </a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-navigator-extension:-requestmediakeysystemaccess()">
   <a href="https://www.w3.org/TR/encrypted-media/#navigator-extension:-requestmediakeysystemaccess()">https://www.w3.org/TR/encrypted-media/#navigator-extension:-requestmediakeysystemaccess()</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-navigator-extension:-requestmediakeysystemaccess()">5. 
    Polyfills and Backward Compatibility </a>
    <li><a href="#ref-for-navigator-extension:-requestmediakeysystemaccess()①">6.2. 
        User Consent </a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-media-data">
   <a href="https://www.w3.org/TR/html51/semantics-embedded-content.html#media-data">https://www.w3.org/TR/html51/semantics-embedded-content.html#media-data</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-media-data">2. 
    Algorithm Extensions </a> <a href="#ref-for-media-data①">(2)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-idl-DOMString">
   <a href="https://heycam.github.io/webidl/#idl-DOMString">https://heycam.github.io/webidl/#idl-DOMString</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-idl-DOMString">1. 
    MediaKeySystemMediaCapability dictionary extension </a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-dfn-present">
   <a href="https://heycam.github.io/webidl/#dfn-present">https://heycam.github.io/webidl/#dfn-present</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dfn-present">1. 
    MediaKeySystemMediaCapability dictionary extension </a> <a href="#ref-for-dfn-present①">(2)</a> <a href="#ref-for-dfn-present②">(3)</a> <a href="#ref-for-dfn-present③">(4)</a>
    <li><a href="#ref-for-dfn-present④">5. 
    Polyfills and Backward Compatibility </a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="term-for-dfn-present">
   <a href="https://heycam.github.io/webidl/#dfn-present">https://heycam.github.io/webidl/#dfn-present</a><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dfn-present">1. 
    MediaKeySystemMediaCapability dictionary extension </a> <a href="#ref-for-dfn-present①">(2)</a> <a href="#ref-for-dfn-present②">(3)</a> <a href="#ref-for-dfn-present③">(4)</a>
    <li><a href="#ref-for-dfn-present④">5. 
    Polyfills and Backward Compatibility </a>
   </ul>
  </aside>
  <h3 class="no-num no-ref heading settled" id="index-defined-elsewhere"><span class="content">Terms defined by reference</span><a class="self-link" href="#index-defined-elsewhere"></a></h3>
  <ul class="index">
   <li>
    <a data-link-type="biblio">[encrypted-media]</a> defines the following terms:
    <ul>
     <li><span class="dfn-paneled" id="term-for-clear-key" style="color:initial">Clear Key</span>
     <li><span class="dfn-paneled" id="term-for-get-supported-capabilities-for-audio-video-type" style="color:initial">Get Supported Capabilities...</span>
     <li><span class="dfn-paneled" id="term-for-dom-mediakeysystemaccess" style="color:initial">MediaKeySystemAccess</span>
     <li><span class="dfn-paneled" id="term-for-dom-mediakeysystemmediacapability" style="color:initial">MediaKeySystemMediaCapability</span>
     <li><span class="dfn-paneled" id="term-for-dom-mediakeysystemaccess-getconfiguration" style="color:initial">getConfiguration()</span>
     <li><span class="dfn-paneled" id="term-for-navigator-extension:-requestmediakeysystemaccess()" style="color:initial">requestMediaKeySystemAccess()</span>
    </ul>
   <li>
    <a data-link-type="biblio">[html51]</a> defines the following terms:
    <ul>
     <li><span class="dfn-paneled" id="term-for-media-data" style="color:initial">media data</span>
    </ul>
   <li>
    <a data-link-type="biblio">[WebIDL]</a> defines the following terms:
    <ul>
     <li><span class="dfn-paneled" id="term-for-idl-DOMString" style="color:initial">DOMString</span>
     <li><span class="dfn-paneled" id="term-for-dfn-present" style="color:initial">not present</span>
     <li><span class="dfn-paneled" id="term-for-dfn-present①" style="color:initial">present</span>
    </ul>
  </ul>
  <h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
  <h3 class="no-num no-ref heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
  <dl>
   <dt id="biblio-encrypted-media">[ENCRYPTED-MEDIA]
   <dd>David Dorwin; et al. <a href="https://www.w3.org/TR/encrypted-media/">Encrypted Media Extensions</a>. 18 September 2017. REC. URL: <a href="https://www.w3.org/TR/encrypted-media/">https://www.w3.org/TR/encrypted-media/</a>
   <dt id="biblio-html51">[HTML51]
   <dd>Steve Faulkner; et al. <a href="https://www.w3.org/TR/html51/">HTML 5.1 2nd Edition</a>. 3 October 2017. REC. URL: <a href="https://www.w3.org/TR/html51/">https://www.w3.org/TR/html51/</a>
   <dt id="biblio-rfc2119">[RFC2119]
   <dd>S. Bradner. <a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a>
   <dt id="biblio-webidl">[WebIDL]
   <dd>Boris Zbarsky. <a href="https://heycam.github.io/webidl/">Web IDL</a>. 15 December 2016. ED. URL: <a href="https://heycam.github.io/webidl/">https://heycam.github.io/webidl/</a>
  </dl>
  <h2 class="no-num no-ref heading settled" id="idl-index"><span class="content">IDL Index</span><a class="self-link" href="#idl-index"></a></h2>
<pre class="idl highlight def"><c- b>partial</c-> <c- b>dictionary</c-> <a class="idl-code" data-link-type="dictionary"><c- g>MediaKeySystemMediaCapability</c-></a> {
  <a class="idl-code" data-link-type="interface" href="https://heycam.github.io/webidl/#idl-DOMString" id="ref-for-idl-DOMString①"><c- b>DOMString</c-></a>? <a data-default="null" data-type="DOMString? " href="#dom-mediakeysystemmediacapability-encryptionscheme"><code><c- g>encryptionScheme</c-></code></a> = <c- b>null</c->;
};

</pre>
  <h2 class="no-num no-ref heading settled" id="issues-index"><span class="content">Issues Index</span><a class="self-link" href="#issues-index"></a></h2>
  <div style="counter-reset:issue">
   <div class="issue"> A registry should be created for encryption schemes, and the
    existing format registry should be updated with respect to encryption
    schemes. <a href="https://github.com/wicg/encrypted-media-encryption-scheme/issues/#9">&lt;https://github.com/wicg/encrypted-media-encryption-scheme/issues/#9></a><a href="#issue-7472f44c"> ↵ </a></div>
   <div class="issue"> Publish and link to a polyfill for this feature. <a href="https://github.com/wicg/encrypted-media-encryption-scheme/issues/#13">&lt;https://github.com/wicg/encrypted-media-encryption-scheme/issues/#13></a><a href="#issue-74d893e8"> ↵ </a></div>
  </div>
  <aside class="dfn-panel" data-for="dom-mediakeysystemmediacapability-encryptionscheme">
   <b><a href="#dom-mediakeysystemmediacapability-encryptionscheme">#dom-mediakeysystemmediacapability-encryptionscheme</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme">1. 
    MediaKeySystemMediaCapability dictionary extension </a> <a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme①">(2)</a> <a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme②">(3)</a> <a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme③">(4)</a>
    <li><a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme④">2. 
    Algorithm Extensions </a>
    <li><a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑤">4. 
    Application Notes </a>
    <li><a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑥">5. 
    Polyfills and Backward Compatibility </a> <a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑦">(2)</a> <a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑧">(3)</a> <a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme⑨">(4)</a> <a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme①⓪">(5)</a> <a href="#ref-for-dom-mediakeysystemmediacapability-encryptionscheme①①">(6)</a>
   </ul>
  </aside>
  <aside class="dfn-panel" data-for="cenc">
   <b><a href="#cenc">#cenc</a></b><b>Referenced in:</b>
   <ul>
    <li><a href="#ref-for-cenc">3. 
    Clear Key Requirements </a>
   </ul>
  </aside>
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